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<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <!-- <script src="./js/jquery.js"></script> -->
    <script src="./js/zepto.js"></script>
    <style>
      div {
        width: 200px;
        height: 200px;
        background-color: green;
        margin: 10px;
      }
    </style>
  </head>
  <body>
    <button id="btn">改变第二个标签的颜色</button>
    <div></div>
    <div></div>
    <script>
      $(function () {
        $("#btn").on("click", function () {
          $("div").eq(0).css({
            backgroundColor: "red",
          });
        });
      });
    </script>
  </body>
</html>
